<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .a {
            font-weight: bold;

            color: red;
        }
        .b {

            color: blue;
        }
    </style>
</head>
<body>
<div class="b a">aaaa</div>
</body>
</html>